This project aims to study the molecular structure of the oligomeric enzyme RNA polymerase from E. coli and the structural basis for some of its interactions with templates, substrates, products and effectors. This is achieved by a combination of high resolution electron microscopy (CTEM and STEM) and analog and digital image processing techniques applied to ordered polymers or two-dimensional crystalline arrays of native and specifically labeled core and holoenzyme. Specific labels include subunit-, template-, substrate-, Product-and effector-specific antibody fragments and heavy metal labeled derivatives of these interacting molecules.